Circuit controller



A u 4N ov. 5, 1935. N.' c. scHr-:LLENGR 2,020,001

vCIRCUII' CONTROLLER Original File-d March 51, 1932 HII Hill trollers.

connection between coils of the different resistance wires in order to Patented Nov. 5, 1935 y 2,020,001 PATENT OFFICE CIRCUIT CONTROLLER Newton C. Schellenger,

Chicago Telephone S Ind., a corporation of Elkhart, Ind., assignor to upply Company, Elkhart,

Indiana Original application March 31, 1932, Serial No.

Divided and this application March Thisinvention relates to circuit controllers, and

is more particularly directed to the resistance strips employed in connection with such con- The present application isa division of my copending application, Serial No. 602,362, filed March 31, 1932, which is a division of my copending application, Serial No.'518,281, led February 25, 1931, and in its preferred is directed tothe type of variable prising a. resistance embodiment, resistor comwire wound upon a flat strip for bar of insulating material commonly referred to as the resistance strip, which strip is brought to a cylindrical shape substantially concentric with a shaft upon which a contact arm is affixed, the individual turns of the resistance strip being progressively engaged by means of the contact shoe carried by the arm. l

The resistance wire of the present invention is adapted to be engaged along the flattened surface of the strip, the contact being along the length of la turn of wire lying in the plane of the strip, and not' along the edge of the strip, as

is the usual practice.

I have found that the coils of the resistance wire along the wide cylindrical surfaces adjacent the edges of the resistance strip .are held securely and are more nearly uniform in height and spacing than those on the edge of the strip.- The strip may be also held in a cylindrical con-'- figuration without altering the uniformity of the winding on the inner cylindrical surface, which is engaged by the contacting means.

One object of the present invention is to pro- -vide a resistance strip which may include several wires having different current conducting capacities, the relative length of each wire being varied as desired. By the use of wires of varying resistance characteristics, it is possible to gain an increased flexibility of resistance gradients. In connection with this feature, the application is particularly directed to the manner of providing the respectively adjacent effect a permanent electrical connection therebetween, and to provide a s mooth and graduated resistance change shoe engaging the resistance strip.

,The present invention is further characterized by the provision of a n'ovel insulating strip for winding the resistance wire thereon, this strip being constructed preferably from insulating nbre, phenolic condensation products, or the like,-

by means of the contactingV plished either adjacent turns in the accurate placing of the individual turns of the wire. Preferably, the strip is provided with spaced grooves along its edges, and the resistance wire is placed in these grooves when Wound upon the strip in order to provide accurate spacing between the respective turns of the wire.

The grooves formed on the edge of the strip may be, relative to the diameter of the wire, quite deep, and wire turns along the central' part of the at side of the strip may be secured in position by depositing a suitable cement along the center of each side of the wound strip. This cement is applied after the winding of the wire upon the strip, and upon setting or hardening, the cement forms a definite tie betweenV the coil and theside of the strip, which serves to anchor .the turns against any lateral shifting when engaged by the contactor. This cement is preferably a dense cellulose cement and possesses great strength, but is not brittle upon setting. Bending of the strip into arcuate form does not the central parts of cause the cement to crack or split from between the coils.

If desired, the strip maynot be provided with grooves at the edges thereof, but in such cases, I preferalso to provide a line or band of cement along each edge, in order to .assure that'the wire is Wound upon the str'p and is anchored against any possibility of lateral shifting.

Another feature of the present invention is the provision of a resistance strip which may be wound with wire of different diameters at different points along the lineal extent thereof, which are joined for effecting a smooth and positive engagement of the contacting means therewith. This engagement is particularly achieved when the resistance strip is used in connection with the contacting means described in my abovementioned copending application Serial No. 518,281. The windings are joined or bonded to each other by the use of a small piece of soft metal foil, which is provided at the junction of the windings, and which bridges a suiciently large number of the turns to make a good con nection.

The method of bonding disclosed in the present invention is distinctly advantageous in connection with this typeof resistance strip. This comprises placing a small piece of lead wire over the point of juncture, and then pressing the wire or foil into engagement with the wires and embedding them in the foil. This may be accommanually or automatically. In manual operation, the foil is first threaded under of the winding, and then the upper portion is looped over the underlying portion and pressed into position.

Another feature embodied in the resistance strip of the present invention is the particular construction provided at the terminal ends of the strip, whereby a large number of the turns adjacent each of the ends of the strip are shortcircuited, as by means of metal foil or the like, in

order to provide a good contacting engagement with the base of the terminal member positioned thereabove, this construction being such that no change of resistance can be effected until after the contacting means has left the portion of the resistance strip lying under the terminal member.

Numerous other objects and advantages of the present invention will appear more fully from the following detailed description, which, taken in connection with the accompanying drawing, will disclose to those skilled in the art the particular construction, and method of securing the features set out above.

In the drawing:

Figure 1 is a rear elevational view of a resistance strip embodying one feature of my invention;

Figure 2 is an elevational view of a resistance strip provided with a terminal member for connecting the strip to an external circuit;

' Figure 3 is an elevational View of a strip, embodying several features of the invention;

Figure 4 is a fragmentary diagrammaticv sectional view, taken substantially on the line 4--4 of Figure 1 and showing the method of joining adjacent turns of two different kinds of wire for providing a junction therebetween;

Figure 5 is a fragmentary sectional view taken substantially on the line 5-5 of Figure 3, and showing a different method of performing the same connecting operation;

Figure 6 is an enlarged fragmentary detailed sectional View showing the terminal assembly disclosed in Figure 2;

Figure 7 is an enlarged fragmentary detail View of the resistance strip, disclosing the grooves formed in the edges thereof for securing the turned wire in spaced relation; and

Figure Sis' a sectional view taken substantially on the line 8-8 of Figure 2.

Referring now in more detail to the drawing, in Figure 1 I have disclosed an insulating member, indicated at 5, which is preferably composed of a strip of laminated phenolic compound of a special composition, which renders the same sufciently flexible to permit bending when hot of the relatively short length which is employed into cylindrical shape, in order to accommodate the resistance within a cup-shaped housing.

The'strip 5 maybe formed from any suitable insulating material, such as bre or the like, if

desired. The edges 6 and 'I ofthe strip are preferably rounded, and are trued with respect to each other to provide parallel surfaces. The ends ofthe strip 5 are preferably notched, as

indicated at 8, for accommodating a rivet or ,oth-

er suitable securing means when the strip is bent into cylindrical form, for securing the resistance strip in-xed position within the housing of the rheostat. The particular manner of securing the resistance strip, by means of the notches formed in the abutting edges thereof, is described in detail in my copending application, Serial No. 518,281, led February 25, 1931.

Upon the strip 5 is preferably wound a resistance wire, indicated at 9, which is of relatively small diameter, for example, .002 of an inch, and which extends along the strip for a substantial length thereof. The wire is bare, and is spaced approximately .0001 of an`inch between turns, which provides for approximately 466 turns per the strip, this wire possessing different current 5 carrying characteristics than the wire 9, and may, or may not be, of the same diameter. The two windings 9 and I0 meet at a point adjacent that indicated by the reference numeral II, and are suitably connected together by means of the metal 10 foil member I2.

Referring now in detail to Figure 4, which illustrates one method of connecting the windings 9 and IIB, I have disclosed therein a strip of metal foil I2, which is preferably of soft metal, such l5 as lead or the like, the strip having one end thereof threaded, as by means of a needle or the like,

' under the adjacent pairs of turns' of the windings 9 and I0. This portion of the metal foil is indicated by the numeral I3. After the portion 20 I3 has been inserted under the respective pairs of turns of the windings 9 and I0, the remaining portion of the foil member I2 is bent over, as indicated in dotted lines in Figure 4, and engages the upper surfaces of the windings. Suitable 25 pressure may then be applied, either by means of a press, or by means of the compressive expansion of the resistance strip within the housing .by means of the securing rivet, as described in my copending application, Serial No. 518,281; 30

' led February 25, 1931, for pressing the metal foil member firmly about the turns of the windings, in order that good electrical contact may be made therebetween. The foil member, being made of relatively soft metal, is easily pressed 35 downwardly so as to fill up the interstices between the adjacent turns of the windings and to afford a compact and effective connecting means.

Considering now Figure 2, it will be noted that the resistance strip is similar to the resistance 40 strip 5 of Figure l, and has been correspondingly identified. In order to assure that the winding of the resistance wire will be accurately held in spaced relationship upon the resistance strip during movement ofthe contacting means, I prefer- 4,', ably provide a band of cement, indicated by the numeral I4, along the central part of the flat side of the strip. If desired, similar bands of cement I5 and I6 may bev provided along the edges 6 and 'I of the strip for further assuring that the indi- 50 vidualturnsrof the resistance wire will be held in properl spaced relationship. Preferably bare wire is employed, as with .the method of making contact disclosed in my copending application Serial No. 518,281, bare wirewith very little space be- 55 tween the respective., turns thereofis entirely feasible, and there isrnot the difficulty of removing the enamel, or other insulation, which is the case in rheostats where enameled wire or the like is employed. The cement used for providing the 60 bands I4, I5 and I6, is preferably a tough, dense cellulose cement that possesses great binding strength, but does not become brittle upon hardening. Thus, bending of the strip 5 into arcuate form after winding will not cause the cement to 65 crack or split from between the coils of the winding.

Considering now the left hand end of the strip 5 of Figure 2, it will be noted that a plurality of the individual turns II of the resistance wire 70 wound upon the strip are covered by a soft metal foil member I8, which, as shown more clearly in Figures 6 and 8, is pressed down about each of the turns I1 of the winding, and completely fills the spaces between adjacent turns. This foil 75 provided a resistance coins resistance wire winding.

member Il may be pressed into engaging relation with the turns I1 either by hand or by a machine `strip, and' in place thereof the edges are provided with spaced grooves 35, 'these grooves 35 being adapted to receive the individual turns 36 of the It desired, cement may also be applied to the wire winding turns thereof, in proper spaced relationship. As shown in m re detail in Figure 8, the edges of the insulator strip 5 are rounded. in order to presharp corners` to the wire being wound thereon.

It is apparent that the wire maybe held in spaced relation along the strip by means of either cement, disposed along the iiat surface 0i' the application, l

to either situation. Also, the composition of the strip, together with the ce- 1o menting means used in connection with tlie winding, permits the strips to be bent into cylindrical I do not intend to be iimited to the exact dev tails shown anddescribed in the illustrated em- 25 bodiment oi' my invention,

but only in so far as .deiined by the scope and spirit of the appended claims.

ing material, lapping a. portion of said foil over said turns, and pressing both portions of the ioil 35 into'irm engagement with said turns.

2. The method of joining two coils of wire wound upon insulating material f material to press the metal around the adjacent peripheries of each oi.' the windings.

5. The method of joining adjacent turns of two 

